Glass solders are used in the related art, among other things, for sealing between components and for electrical insulation. In the industrial field, glass solders are used in photovoltaics and in fuel cell technology, for example. Molten glass solders are used there to connect individual cells and other components in series and to separate these from each other electrically, and in an mechanically gastight manner. This covers, for example, metallic or ceramic interconnectors, cells, as well as base and cover plates.
Commonly used methods for applying a glass solder onto a substrate are the screen printing technique, dispensing methods, and the tape casting technique. Screen printing, generally speaking, involves printing the printing ink through a fine-meshed fabric onto the material to be imprinted, using a squeegee. The mesh apertures of the fabric are rendered impermeable to the ink by a stencil in those areas of the fabric where, in keeping with the print image, no ink is to be transferred. The technique has been previously published for the production of fuel cell stacks and for the production of photovoltaic cells.
It is also known to produce ceramic green tapes using a tape casting method. It is known from US 2009/0004544 A1 to produce green seals from such tapes by way of stamping.
Tape production by way of casting has the drawback that it is relatively complex, and the required stamping tool is significantly more expensive than a printing screen. The actual seal accounts for only a small surface proportion of the tape used in the stamping process, and the majority of the paste disadvantageously becomes stamping scrap. This scrap, in turn, is only conditionally reusable, since consistency in the formulation requires that the same proportion is used at all times, and additionally, reprocessing the scrap necessitates special measures. When a tape that is commercially available in the market is to be used, the formulation of the same is generally not known. A comparison of the costs that are incurred in the production of green seals using the two methods shows that tape casting is considerably more expensive than screen printing.
The drawback of the screen printing method is that uneven shapes are difficult to imprint with the paste, since no uniform layer thickness can be created. This drawback is particularly significant when thick layers are applied to a component so as to be bonded to another component.